Power supply unit

ABSTRACT

A power supply unit for supplying power to a device has a rechargeable, main battery; a charging arrangement for charging the main battery; a non-rechargeable back-up battery; load terminals for connection to a load; and a control unit for controlling supply of power to the load primarily from the main battery and secondarily from the back-up battery. The device is, in particular, a single bay, stand alone parking meter. In the event that the main battery runs low, the control unit is configured to supply power to the load from both the main battery and the back-up battery or only from the back-up battery. The back-up battery is easily replaceable, and the power supply unit has a bay, with connectors for receiving the back-up battery. The main battery is charged from solar panels. A communication device is provided to communicate status messages wirelessly to a control system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/909,209, filed Mar. 30, 2007, by Hunter et al., entitled POWER SUPPLYUNIT, and is a continuation of U.S. Application No. 12/059,909, filedMar. 31, 2008, each of which is incorporated in its entirety herein byreference.

FIELD OF THE INVENTION

THIS INVENTION relates to a power supply unit and to a device, inparticular a single bay parking meter, having the power supply unit.

SUMMARY OF THE INVENTION

According to the invention, there is provided a power supply unit forsupplying power to a device, the power supply unit including

a rechargeable, main battery;

a charging arrangement for charging the main battery;

a set of connectors for connection to a back-up battery;

a set of load terminals for connection to a load; and

a control unit for controlling supply of power to the load primarilyfrom the main battery and secondarily from the back-up battery.

In an embodiment of the invention the power supply unit has the mainbattery and the back-up battery. The back-up battery is preferablynon-rechargeable.

It will be appreciated that power is taken, in use, from the backupbattery in the event that the main battery is inadequate.

Further according to the invention there is provided a device, inparticular a parking meter, which has a power supply unit in accordancewith the invention.

In the event that the main battery runs low, the control unit isconfigured to supply power to the load from both the main battery andthe back-up battery or only from the back-up battery.

In a preferred embodiment, the back-up battery is easily replaceable. Inthis embodiment, the power supply unit has a bay for receiving theback-up battery and the connectors are spaced and are such as to permiteasy removal and replacement of the back-up battery.

In another embodiment of the invention, the power supply unit furtherincludes a communication device, for communicating messages to a controlsystem. Such messages are selected from the group consisting of:notification that the main battery has been insufficiently recharged,and a notification that power is being supplied from the backup battery.

In a further embodiment of the invention, the communication device maybe operable in a wireless manner, and utilizes a cellular telephonenetwork. Thus, with this embodiment, the communication device may have acellular telephone module.

In an embodiment of the invention, the charging arrangement includescharging terminals for connecting the unit to a solar panel. The devicethen incorporates the solar panel.

It will be appreciated that in normal operation power is supplied onlyfrom the main battery. However, if the main battery is insufficientlyrecharged, or it is unable to supply the power required by the load,then supplementary power is supplied, partially or totally, from thebackup battery, as determined by the control unit.

Preferably, the nominal supply voltage of the backup battery is slightlygreater than that of the main battery.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention is now described, by way of example onlyand without limiting the scope of the invention, with reference to theaccompanying figures, wherein:

FIG. 1 is an isometric view of a power supply unit in accordance withthe invention, shown in alignment with part of a parking meter body;

FIG. 2 is a rear view of the part of the parking meter body, depictingthe power supply unit when inserted fully therein;

FIG. 3 is a schematic sectioned view of the power supply unit; and

FIG. 4 is a circuit diagram of the power supply unit.

DETAILED DESCRIPTION

In the accompanying figures, the power supply unit is generallydesignated by reference numeral 10 and comprises a rechargeable, mainbattery 12, a charging arrangement in the form of a diode 34 forcharging the main battery 12, a replaceable back-up battery 14, loadterminals 19 and a control unit 16 for controlling supply of power to aload 20 connected via the load terminals 19 primarily from the mainbattery 12 and secondarily from the back-up battery 14 in the event thatthe main battery 12 is inadequate. The power supply unit 10 further hasa solar panel terminal 33 and an auxiliary charging terminal 28.

The power supply unit 10 further includes a bay 17 which contains thereplaceable backup battery 14. The bay 17 is illustrated in FIG. 3,where it is seen to be defined by a compartment 21 with a lid 23 withinthe power supply unit 10. The bay 17 has spaced connectors 15 for thebackup battery 14. Also shown in FIG. 3 is a communication device 24with a cellular telephone module 26.

More specifically, in a preferred embodiment of the invention, the mainbattery 12 comprises an arrangement of five “AA” size nickel cadmiumrechargeable cells, which cells are coupled to each other and rechargedby solar panels 18 via the solar panel terminal 33. The backup battery14 comprises a coupled arrangement of two non-rechargeable, disposable“C” size lithium-thionyl chloride cells, and the control unit 16 is aconventional linear, low dropout control unit, known in the trade as theLinear Technology™ model LT1529-5. The control unit 16 controls thesupply of power to the load 20 from the main battery 12 and the backupbattery 14, in the manner described below.

It is not only the power supply unit 10 itself that is the subject ofthis invention. This invention extends to include a device, inparticular a single bay stand alone parking meter 50, having the powersupply unit 10 as described above. This is illustrated in FIGS. 1 and 2,in which FIG. 1 depicts the power supply unit 10 aligned for insertioninto a complementary dimensioned and configured recess 40 within parkingmeter 50. The power supply unit 10 is moved into position, in thedirection of arrow “A,” to fit snugly within the recess 40, as isdepicted in FIG. 2. A coin validation unit 45 of the parking meter 50 isnot a part of the present invention, but is mentioned for completeness,since the validation unit 45, and other components, such as a timer anda display (not shown) are powered by the power supply unit 10, beingconnected thereto via the load terminals 19. The parking meter 50 hasthe solar panels 18 which are connected to the solar panel terminal 33.

The power supply unit 10 is operated as follows. Under favorableconditions, with the main battery 12 being sufficiently charged and withthe voltage across the main battery 12 being greater than apredetermined threshold value, the control unit 16 is configured topermit only the main battery 12 to supply power to the load 20.Conversely, under unfavorable conditions, when the main battery is notsufficiently charged, the supply voltage of the main battery 12 is lowerthan the threshold value, and in such conditions, the control unit 16 isconfigured to permit power to be supplied also, or only, from the backupbattery 14 to the load. It will be appreciated that, in this way, use ofthe backup battery 14 occurs only when strictly necessary, namely whenthe voltage across the main battery 12 falls below a predeterminedlevel.

In the particular instance where the power supply unit 10 is for a standalone parking meter, the nominal supply voltage of the main battery 12is 6.0V and of the back-up battery 14 7.2V. The control unit 16 isconfigured to permit power to be supplied from the backup battery 14when the voltage across the main battery 12 measures 5.5 V or less.

Capacitor 30 is provided to assist during peak power demand andcapacitor 22 assists with stability of the regulator 16 and with peakpower demand. In alternative embodiments of the invention, a further,external recharging source, such as a portable charger, may be connectedvia terminal 28. It will be appreciated that the extent of reliance onthe backup battery 14 to supply current to circuit 20, is minimized.This, in turn, extends the lifespan of the backup battery 14.

The power supply unit 10 further includes diodes 34 and 36, which serveto prevent reverse current from flowing into the solar panels 18 and anexternal auxiliary recharging source via terminal 28 respectively.

The communication device 24 communicates notifications to a controlsystem (not shown). Typically, such notifications relate to the state ofthe main battery 12 and of the backup battery 14. Notifications that arecommunicated are that the voltage across the main battery 12 has fallenbelow the predetermined minimum level, and that power is being suppliedfrom the backup battery 14. The communication device 24 communicatesthese notifications in a wireless manner across a telecommunicationsnetwork via the cellular telephone module 26.

It will be appreciated by the person skilled in the art that applicationof this invention is not limited to parking meters only, but that thisinvention also has application to a multitude of power supply units usedto supply current to electrical circuits.

1.-17. (canceled)
 18. A method for controlling the supply of power to aparking meter comprising: a) monitoring, by a control unit, the statusof a rechargeable main battery and a back-up battery; b) supplyingpower, by the control unit, to the parking meter primarily from the mainbattery; c) switching the supply of power, by the control unit, to comefrom the back-up battery when the voltage across the main battery fallsbelow a predetermined level; d) supplementing the supply of power duringa peak power demand, by the control unit, to the main battery byutilizing at least one capacitor; and e) signaling, by the control unit,a wireless communication device to communicate a status message to acontrol system external to the parking meter regarding the state of themain battery and the back-up battery; provided that the main battery,the back-up battery, the at least one capacitor, the wirelesscommunication device, and the control unit are received within theparking meter.
 19. The method of claim 18, wherein the status messagecomprises one or more of: battery charge rate, remaining battery charge,remaining battery life, real-time current supplied by solar cell,average current supplied by solar cell, resistance at various sectionswithin the power supply, error messages indicating battery failure,error messages indicating solar panel failure, real-time powerconsumption, and average power consumption.
 20. The method of claim 18,wherein the status message is communicated over a telecommunicationsnetwork.
 21. The method of claim 18, further comprising switching thesupply of power, by the control unit, back to the main battery when themain battery is sufficiently recharged.
 22. The method of claim 21,further comprising minimizing the supply of power from the back-upbattery after switching the supply of power to come from the mainbattery.
 23. The method of claim 18, wherein the rechargeable mainbattery consists of one to five cells.
 24. The method of claim 18,wherein the replaceable back-up battery consists of one to five cells.25. The method of claim 18, wherein the at least one capacitor consistsof two to five capacitors.
 26. The method of claim 18, wherein the atleast one capacitor comprises an ultra-capacitor.
 27. The method ofclaim 18, wherein the at least one capacitor is in parallel with themain battery.
 28. The method of claim 18, wherein a first capacitor isconnected in parallel with the main battery to assist the main batteryduring the peak power demand, and a second capacitor is connected inparallel with the back-up battery to assist the back-up battery duringthe peak power demand.
 29. The method of claim 18, wherein the peakpower demand is during start up of the parking meter.
 30. The method ofclaim 18, wherein the peak power demand is during start up of thewireless communications device.
 31. The method of claim 18, wherein theparking meter further comprises a solar panel connected to the mainbattery and the back-up battery.
 32. The method of claim 31, wherein themain battery is recharged by the solar panel.
 33. The method of claim31, wherein the parking meter further comprises a diode coupled to thesolar panel to prevent reverse current from flowing into the solarpanel.
 34. The method of claim 18, wherein the back-up battery isrechargeable.
 35. The method of claim 18, wherein the predeterminedlevel is 5.5V.
 36. A power supply for supplying power to a parking metercomprising: a) a rechargeable main battery; b) a replaceable back-upbattery; c) at least one capacitor; d) a connection to a wirelesscommunication device for communicating a status message regarding thestate of the main battery and the state of the back-up battery to acontrol system external to the parking meter; and e) a connection to acontrol unit for controlling supply of power to the parking meterprimarily from the main battery and secondarily from the back-upbattery, wherein the at least one capacitor assists during a peak powerdemand; provided that the main battery, the back-up battery, the atleast one capacitor, the wireless communication device, and the controlunit are received within the parking meter.
 37. The power supply ofclaim 36, wherein the wireless communication device communicates statusmessages to the control system, the status messages comprising one ormore of: battery charge rate, remaining battery charge, remainingbattery life, real-time current supplied by solar cell, average currentsupplied by solar cell, resistance at various sections within the powersupply, error messages indicating battery failure, error messagesindicating solar panel failure, real-time power consumption, and averagepower consumption.
 38. The power supply of claim 36, further comprisinga solar panel connected to the main battery and the back-up battery. 39.The power supply of claim 38, wherein the main battery is recharged bythe solar panel.
 40. The power supply of claim 36, wherein the peakpower demand is during start up of the parking meter.
 41. The powersupply of claim 36, wherein the peak power demand is during start up ofthe wireless communications device.
 42. The power supply of claim 36,wherein the at least one capacitor comprises an ultra-capacitor.